These studies are designed 1) to improve understanding of the biologic implications of circualating parathyroid fragment; and 2) to apply the radioimmunoassay of PTH to the study of disease. A systematic investigation of PTH metabolism in liver and kidney is proposed; isolated, perfused organs will be used. This approach permits delineation not only of rates of generation of various metabolites, but also factors controlling these rates. In addition, the organ perfusion systems may make possible the generation of sufficient quantities of metabolites for testing in various biologic systems, purification, and production of specific antibodies. Efforts will be made to develop a receptor site assay using renal cortical tissue. The major thrust of clinical investigations will include attempts to prevent early and to reverse established renal hyperparathyroidism. The mechanism of hyperparathyroidism in idiopathic hypercalciuria will be studied further.